1. Field of the Invention
The present invention relates to a method and an apparatus for processing a silicon wafer containing oxygen that involves controlling defect density within the silicon wafer. The present invention particularly relates to a method of processing a silicon wafer that involves suppressing or inducing oxygen precipitation within the silicon wafer, and a method of manufacturing a semiconductor device that uses a silicon wafer that is processed by such a method.
2. Description of the Related Art
Presently, a wafer manufactured through the Czochralski (CZ) method is widely used as a wafer for a silicon device (also referred to as CZ wafer hereinafter).
Generally, a silicon wafer manufactured through the CZ method includes oxygen that is dissolved into growing silicon from quartz crucibles during silicon crystal growth to be incorporated into silicon crystals. In such a silicon wafer, oxygen precipitates (silicon oxide precipitates in single crystal silicon) are generated during the cooling stage of crystal growth and during the heating and cooling stages of a device manufacturing process, for example. It is noted that a strain field (stress field) is generated around the oxygen precipitates owing to their volume difference with the silicon matrix. Such a strain field has an effect of attracting and capturing heavy metal atoms which effect is referred to as intrinsic gettering (simply referred to as gettering hereinafter).
It is noted that heavy metal atoms residing within an active layer of the silicon device may cause leak currents and malfunction of the device. Although cleaning is performed in the device manufacturing process to reduce the heavy metal atoms, the heavy metal atoms are inevitably introduced into the device through the muffle of an oxidation/diffusion furnace, for example. Therefore, gettering by the silicon wafer is necessary (e.g., see K. Sueoka, Journal of Electrochemical Society, 152, G 731, 2005).
A semiconductor integrated circuit may be manufactured by depositing various thin films such as an insulating film, an electrode, wiring, and an interlayer film on a CZ wafer. In this film deposition process, the silicon wafer is heated to a high temperature upon having the films deposited thereon so that heat stress may be generated upon cooling the silicon wafer after the film deposition owing to the difference in the thermal expansion coefficients between the thin films and silicon. It is noted that the silicon wafer may also be heated during processes other than the film deposition process such as an impurity diffusion process. By heating the silicon wafer in the manner described above, a varied temperature distribution especially in the radial direction may be created within the silicon wafer and heat stress may be generated as a result.
It is noted that in most cases, such heat stress includes shear properties that may cause the occurrence of slip and diffusion. A slip generally occurs from a wafer supporting position at which the silicon wafer is supported upon being heated. Such a slip within the wafer may cause device malfunctions such as leakage, and therefore, various measures have been developed for preventing the occurrence of slip and diffusion within the silicon wafer. A technique of controlling slip diffusion with oxygen precipitates residing within a CZ wafer has been developed as one example of such measures. As can be appreciated from the above descriptions, oxygen precipitates may be used to control slip diffusion in addition to functioning as a gettering site (e.g., see K. Yasutake, M. Umeno, and H. Kawabe, Applied Physics Letters, 37, 789, 1980).
As is described above, oxygen precipitates are necessary for ensuring reliability and a high production yield of the silicon device. However, with the growing trend toward device miniaturization and reduction of the processing temperature, it is becoming difficult to realize adequate oxygen precipitation during a heating process. In turn, device performance may be degraded and the production yield may be decreased due to impurities residing within the wafer and slip occurring within the wafer. Accordingly, techniques are in demand for efficiently generating oxygen precipitates within a wafer in a heating process with reduced processing temperature.